1. Field of the Invention
This invention relates to a process and apparatus for a radiant gas burner in which a combustion flame is stabilized completely within a porous matrix bed of the radiant gas burner.
2. Description of Prior Art
Conventional gas-fired infrared burners use flame energy or hot gases to heat a radiating refractory or other suitable heat transfer material and thus produce a relatively flat flame on and/or above a radiating surface of the burner. Radiant tube burners have internally fired radiation units in which a radiating surface is interposed between a flame and a load. Surface combustion infrared burners have a radiating surface with a porous refractory through which a combustion mixture is passed and then burned above the surface to heat the surface by conductive heat transfer. Gas-fired infrared generators have a burner with a radiating refractory surface which is heated directly with a gas flame. Also, other infrared generators use a porous catalyst bed to oxidize fuel at a relatively low temperature in a low-temperature catalytic burner.
U.S. Pat. No. 4,643,667 discloses a non-catalytic porous-phase combustor and process for generating radiant heat energy. A gas phase reaction and combustion occur within pores of a multi-layer porous plate. The combustible fuel mixture is introduced through an inlet and then distributed within a distribution chamber. The combustible fuel mixture then enters a porous low-thermal conductivity layer which is heated through conduction heat transfer from combustion within a high-thermal conductivity layer. According to the '667 patent, a thermal gradient is established within the low-thermal conductivity layer, with the lowest temperature at the interface of the low-thermal conductivity layer. The highest temperatures occur at an interface between the low-thermal conductivity layer and a contiguous high-thermal conductivity layer.
U.S. Pat. Nos. 4,666,400, 4,605,369 and 4,354,823 disclose various radiant burners in which combustion occurs at a face or outside surface of a gas permeable matrix. Such surface combustion produces results which significantly differ from combustion stabilized within a porous matrix bed.
U.S. Pat. No. 4,416,618 teaches a gas-fired infrared generator with porous ceramic fiber panels. A combustion mixture flows through the fiber panels and is combusted on the surface of the panels. U.S. Pat. No. 3,188,366 discloses a heating process in which a mixture of combustible gases passes through porous refractory material and is combusted at or above the surface, forming a continuous mantle of flameless high-temperature flue gases.
U.S. Pat. Nos. 4,673,349, 3,833,338 and 4,597,734 each disclose a surface combustor. According to the '349 patent, combustion occurs at the surface of a burner plate. According to the '338 patent, an air-gas mixture is combusted at the surface of a cloth or blanket. The '734 patent teaches combustion occurring at a surface of a porous element. None of such patents either teach or suggest stabilizing combustion within a porous matrix bed.
U.S. Pat. Nos. 4,529,123 and 4,673,350 each disclose radiant heating systems which do not include a porous matrix distributor for the combustible gases. U.S. Pat. Nos. 4,608,012 and 4,610,623 each disclose gas burners. The '012 patent discloses a plaque of ceramic foam material and combustion occurs at the surface of such ceramic foam material.
U.S. Pat. No. 4,604,051 discloses a regenerative burner. U.S. Pat. No. 4,599,066 teaches a radiant energy burner in which a combustible fuel mixture is ignited on the outer surface of a fabric. U.S. Pat. No. 3,322,179 discloses a fuel burner with a porous matrix and combustion occurs at the surface of the porous matrix.
U.S. Pat. No. 4,529,374 discloses a gas particulate solid system wherein fuel is supplied to a crater portion of bed material. U.S. Pat. No. 4,878,837 teaches an infrared burner which operates with extremely low overall pressure drop.
As noted from the prior art described above, conventional radiant gas burners operate with combustion and a combustion flame at or above either a radiant surface or a top surface of the porous bed. Other than the '667 patent which suggests flame stabilization in a porous matrix bed which has at least two discrete and contiguous layers, none of the prior art references discussed above either teach or suggest stabilizing a combustion flame within a porous matrix bed to achieve better overall efficiency of the radiant gas burner. None of such prior art references either teach or suggest flame stabilization within a porous matrix bed having only one layer of refractory particles.